The most commonly used method to eliminate residual stress is high-temperature tempering, that is, the weldment is heated to a certain temperature and kept in a heat treatment furnace for a certain time, and the stress is reduced by lowering the yield limit of the material at high temperature, so that plastic flow occurs where the internal stress is high, and the elastic deformation gradually decreases and the plastic deformation gradually increases.

The influence of post-weld heat treatment on the tensile strength and creep limit of metals is related to the temperature and holding time of heat treatment. The effect of post-weld heat treatment on the impact toughness of weld metal varies with different steel grades.

Extended data:

Method selection:

Post-weld heat treatment generally adopts single high-temperature tempering or normalizing plus high-temperature tempering. The gas welding joint adopts normalizing and high temperature tempering heat treatment.

This is because the grains of gas welding seam and heat affected zone are coarse and need to be refined, so normalizing treatment is adopted. However, single normalizing can not eliminate residual stress, and high temperature tempering is needed to eliminate stress.

Single medium temperature tempering is only suitable for the assembly and welding of large ordinary low carbon steel containers assembled on site, and its purpose is to partially eliminate residual stress and dehydrogenation.

In most cases, a single high temperature tempering is selected. The heating and cooling of heat treatment should not be too fast, and the inner and outer walls should be uniform.

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